1. Field of the Invention
The invention relates to an integrated semiconductor circuit having a component formed of a semiconductor substrate with a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type forming an active pn junction therebetween. The integrated semiconductor circuit also has a protective circuit assigned to the component for serving to dissipate overvoltages and/or electrostatic charges.
Integrated semiconductor circuits, in particular fast optoelectronic transmission components such as semiconductor laser circuits or infrared light-emitting diodes are sensitive to electrostatic charges (ESD-Electrostatic Discharge) or voltage spikes in the reverse direction of the pn junction of the transmission component, which may result in damage to, or the destruction of, the component. In order to avoid ESD damage, the known integrated semiconductor circuit has protective circuits formed on the semiconductor substrate of the component and serve to dissipate overvoltages. In particular in the form of protective diodes, which are connected, for example, between a connection point of the active pn junction of the component and earth. The protective circuit is disposed in the immediate vicinity of the component that is to be protected against overvoltages, to be precise on the same semiconductor substrate as the component. The production of the protective circuit on the same substrate can lead to difficulties particularly in the case of optoelectronic transmission components having a semiconductor substrate made of a III-V compound such as, for example, gallium arsenide, indium phosphide and the like. On the one hand, the space available for forming the protective circuit on the semiconductor substrate may be restricted for layout reasons. Furthermore, optoelectronic transmission components, in particular, require, on account of the generally high transmission power, measures for ensuring good dissipation of heat during the operation of the transmission component. In an unfavorable manner, semiconductor materials made of a III-V compound have a much poorer thermal conductivity than silicon, with the result that, in many of such transmission components, a mount which is thermally coupled to the transmission component chip and is made of a material having a low thermal resistance and a large area compared with the chip area of the transmission component is employed in order to ensure good heat dissipation.
From Japanese Patent Abstract No. JP-A-59 188 181 there is disclosed an integrated semiconductor circuit in which a protective diode formed on the semiconductor mount is connected parallel to the active pn-junction. In this manner, the semiconductor mount is to function as a protective circuit for the active component after mounting a reverse voltage on the active pn-junction.